问题描述

我有这段用于从 AVAssetReaderOutput 读取数据的代码片段，该方法在 iOS 4.0 中运行良好，但在 5.0 中它会因访问错误而崩溃，不知道为什么，任何人都有有什么意见吗?

I have this snippet of code used to read data from an AVAssetReaderOutput, the method works fine in iOS 4.0, however in 5.0 it crashes towards the end with bad access, not sure why, anyone have any input?

AVAssetReaderOutput *output=[myOutputs objectAtIndex:0];
 int totalBuff=0;
while(TRUE)
{
     CMSampleBufferRef ref=[output copyNextSampleBuffer];
    if(ref==NULL)
        break;
    //copy data to file
    //read next one
    AudioBufferList audioBufferList;
    NSMutableData *data=[[NSMutableData alloc] init];
    CMBlockBufferRef blockBuffer;
    CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(ref, NULL, &audioBufferList, sizeof(audioBufferList), NULL, NULL, 0, &blockBuffer);

for( int y=0; y<audioBufferList.mNumberBuffers; y++ )
{
    AudioBuffer audioBuffer = audioBufferList.mBuffers[y];
    Float32 *frame = audioBuffer.mData;


    NSLog(@"Gonna write %d", audioBuffer.mDataByteSize);
    //crashes here
    [data appendBytes:frame length:audioBuffer.mDataByteSize];



}

totalBuff++;
CFRelease(blockBuffer);
CFRelease(ref);


   [fileHandle writeData:data];
    [data release];
}

谢谢

丹尼尔

推荐答案

我实际上是通过检查 blockBuffer 是否为 null 来解决这个问题，如果是则继续，问题是 ref 不是 null 但 blockBuffer 是所以这段代码修复了我的问题

I actually fixed this by checking that blockBuffer was null and continuing if it was, the problem was that ref was not null but the blockBuffer was so this code fixed my issue

-(void)doExportSong:(NSURL*)url toFileUrl:(NSString*)fileURL 
{
    AVURLAsset *asset=[[[AVURLAsset alloc] initWithURL:url options:nil] autorelease];
    AVAssetReader *reader=[[[AVAssetReader alloc] initWithAsset:asset error:nil] autorelease];
    [reader setTimeRange:CMTimeRangeMake(kCMTimeZero, kCMTimePositiveInfinity)];
    NSMutableArray *myOutputs =[[NSMutableArray alloc] init];
    for(id track in [asset tracks])
    {
        AVAssetReaderTrackOutput *ot=[AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:track outputSettings:nil];

        [myOutputs addObject:ot]; 
        [reader addOutput:ot];
    }
    [reader startReading];
    NSFileHandle *fileHandle ;
    NSFileManager *fm=[NSFileManager defaultManager];
    if(![fm fileExistsAtPath:fileURL])
    {
        [fm createFileAtPath:fileURL contents:[[[NSData alloc] init] autorelease] attributes:nil];
    }
    fileHandle=[NSFileHandle fileHandleForUpdatingAtPath:fileURL];    
    [fileHandle seekToEndOfFile];

    AVAssetReaderOutput *output=[myOutputs objectAtIndex:0];

    int totalBuff=0;
    BOOL one=TRUE;
    while(TRUE)
    {
        CMSampleBufferRef ref=[output copyNextSampleBuffer];
        // NSLog(@"%@",ref);
        if(ref==NULL)
            break;
        //copy data to file
        //read next one
        AudioBufferList audioBufferList;
        NSMutableData *data=[[NSMutableData alloc] init];
        CMBlockBufferRef blockBuffer;
        CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(ref, NULL, &audioBufferList, sizeof(audioBufferList), NULL, NULL, 0, &blockBuffer);
        // NSLog(@"%@",blockBuffer);

        if(blockBuffer==NULL)
        {

                [data release];
                continue;

        }
        if(&audioBufferList==NULL)
        {
            [data release];
            continue;
        }

        for( int y=0; y<audioBufferList.mNumberBuffers; y++ )
        {
            AudioBuffer audioBuffer = audioBufferList.mBuffers[y];
            Float32 *frame = (Float32*)audioBuffer.mData;


            [data appendBytes:frame length:audioBuffer.mDataByteSize];



        }

        totalBuff++;

        CFRelease(blockBuffer);
        CFRelease(ref);
        ref=NULL;
        blockBuffer=NULL;
        [fileHandle writeData:data];
        [data release];
    }

    [fileHandle closeFile];
    [myOutputs release];  
}

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